Air conditioners are standard equipment of most motor vehicles currently sold. These air conditioners are typically compression systems. These systems employ four elements: a compressor, a condenser, an expansion valve and an evaporator. Heat is absorbed from the cabin space of the motor vehicle when a refrigerant is evaporated in the evaporator. The engine of the motor vehicle typically provides the power to compress the refrigerant vapor prior to it being re-condensed to a fluid in the condenser. The expansion valve is used to reduce the pressure and temperature of the fluid to conditions in the evaporator.
Absorption type air condensers are well known and widely used. In one such widely used system, a strong solution of ammonia, NH3, in water is heated by a gas flame in a container called a generator and NH3 is driven off as a vapor leaving a weak ammonia solution. The NH3 vapor passes into a condenser where it condenses then it flows to an evaporator where it picks up heat from the space being cooled. The NH3 vapor then (instead of being compressed) is reabsorbed into the weak ammonia solution (which in the meantime has been partially cooled) to reform the strong ammonia solution which is returned to the generator to repeat the process. In a Platen-Munters system hydrogen is added to the refrigerant to improve the performance to the system. In these systems pumps are not required to circulate the refrigerant; however, fans or pumps are needed to remove heat in the condenser and in many cases to circulate air in the space being cooled. Absorption type air conditioners are typically not used for motor vehicle air conditioning. However, U.S. Pat. No. 4,307,575 describes an electric vehicle in which the waste heat from the vehicle's electric motor is used to power an absorption type air conditioning unit.
Thermoelectric devices are well known. These devices utilize physics principals known as the Seebeck effect and the Peltier effect. The Seebeck effects refers to a principal underwhich electricity can be generated from a temperature difference and the Peltier effects refers to the opposite effect in which electricity is used to create a temperature difference. U.S. Pat. No. 5,901,527 describes a system in which the Peltier effect is used to cool the sleeping area of a truck. The truck battery is charged up during normal operation of the truck and the battery runs the cooler when the truck is not operating and the driver is sleeping. Another application of thermoelectric devices on motor vehicles is disclosed in U.S. Pat. No. 5,625,245. In this case electricity is generated with thermoelectric modules mounted in a special assembly for converting heat in a trucks exhaust into electric power to charge the trucks battery. Techniques for fabricating thermoelectric modules for electric power generation are described in U.S. Pat. No. 5,875,098. Thermoelectric modules are commercially available from suppliers such as HiZ Corporation with offices in San Diego, Calif. Model HZ14 has dimensions of about 2.5 inches.times.2.5 inches and is about 0.2 inch thick. It produces electric energy most efficiently at about 1.65 volts providing about 14 Watts when provided a temperature difference of about 360 F.
In U.S. Pat. No. 5,449,288 an aspirated wick atomizer nozzle is disclosed for providing high quality combustion of fuels such as diesel fuel for providing a heat source for applications such as thermoelectric power generation. All of the patents referred to in this Background Section are incorporated herein by reference.
Many trucks are provided with sleeper compartments in the cab of the truck. After driving many miles truck drivers can park the truck and sleep before proceeding. In a typical prior art truck air conditioning and heating of the cab including the sleeper section is available only if the engine of the truck is running. If the weather is cold or hot the driver may need to keep the engine running while sleeping. This creates a waste of energy, air pollution, noise, and wear on the engine.
What is needed is a better way to heat and cool a motor vehicle cab when the engine of the vehicle is not operating.